无文件执行程序

参考：

综合利用：Linux系统内存执行ELF的多种方式 https://www.anquanke.com/post/id/168791

perl参考两篇： Linux无文件渗透执行ELF: https://www.secpulse.com/archives/70269.html In-Memory-Only ELF Execution (Without tmpfs)： https://magisterquis.github.io/2018/03/31/in-memory-only-elf-execution.html

PPT: https://2018.zeronights.ru/wp-content/uploads/materials/09-ELF-execution-in-Linux-RAM.pdf

#ifdef HAVE_MEMFD
    #include <sys/mman.h>
#else
    #include <sys/syscall.h>
    #ifndef SYS_memfd_create
        #define SYS_memfd_create 319
    #endif
    #define memfd_create(info_str, flags)   syscall(SYS_memfd_create, info_str, flags)
#endif